level and the projected beams are high enough on the
wall so they also are above eye level, then nobody can get
into a position of looking right at the beams coming out.
A tall wall would be perfect for this.
An alternative would be to project onto a screen from
behind. A label should be prominently displayed on the
outside warning that lasers are involved. A sign at a local
company that uses high power infrared lasers says: “Do
not look into beam with remaining eye!” Check out Sam’s
Laser FAQ ( www.repairfaq.org/sam/lasersam.htm) for a
ton of information on lasers and safety.
The laser diodes need to be mounted in the focusable
housing/heatsink laser holders. Take the housing apart so
you just have the inner brass diode holder. The diodes are
press-fit into the hole in the holder. For me, the hole was a
little too tight, so I filed it out a little until the diode
would fit tightly, but not too tight. I used a drilled-out rod that was wider than the laser diode’s
flange, and the hole inside allowed the diode’s pins
to not have any pressure on them.
My diode pressing tube is shown in Figure 6.
An arbor press was used to push the diode into the
housing with the tubing, or a hammer can be used
to gently tap it in. If it’s too loose, put a rod larger
than the holder’s hole on the inside, take a smaller
rod on the outside, and then with a hammer smash
the edges of the hole a little. This will push some
metal into the hole and tighten it up.
After pressing the diode onto the holder, the
wire leads are soldered to the laser diode, using a
heatsink on the pin near the diode to protect it.
Notice from the diagram in Figure 7 that the pins
are wired differently for the red than for the green
and blue. I used black for negative, and the laser
color for positive.
When it’s put back together, a small drop of oil
on the threads that go into the focusing collar helps
when it comes time to adjust everything. When it
was focused, I put some drops of paint on the
collar and the housing to remember where it was.
I aligned the beams with the disks removed from their
motors, so that the lasers are hitting the wall. Intensity is
set low. A 20” x 30” piece of white foam board makes a
nice display and setup screen for projection from two feet.
(Figure 5 shows the placement of everything.)
The motors were placed on the mounting board first.
Then, back lasers were mounted on the board (two green
and one red). Make sure they’re going in the right
direction and hitting the right location on the disk by
holding up some paper to make sure the beam hits the
right place — preferably while wearing safety glasses.
The outer laser beams are placed at an angle so that
the pattern diverges as it gets farther from the projector,
and the patterns don’t end up on top of each other. A line
was drawn on the board that goes under each laser beam,
which helps keep track of the beam’s location when
44 May/June 2018
■ FIGURE 6. Laser diode mounted in a holder, and
the metal pusher to get the diode into place.
■ FIGURE 7. Wiring of the laser diodes.
■ FIGURE 8. Inside the cover, with the blanket fleece lining
and the acrylic window.